Add create-server acceptance test and support code

This check-in is not complete; it will break acceptance tests.  The
problem is that I cannot run the test in full-quiet mode yet; I need to
support listing of images and flavors before I can do that.  That will
allow the acceptance test to choose a server flavor and OS image
appropriate for the acceptance test.
Merge branch 'master' into create-server

Conflicts:
	interfaces.go
Merge branch 'master' into create-server
Finish acceptance test for CreateServer() function

Two problems remain -- server status is coming up blank, and
measurements of disk and RAM are coming up zeros.  Not sure why this is.
It used to work in Gorax.  More comparative testing between Gorax and
Gophercloud is needed.

However, what is in this commit is sufficient to get the acceptance
tests running again, at least on Rackspace's infrastructure.  If you
attempt to run these tests on HP or other infrastructure, they will
fail for you.
Merge pull request #41 from rackspace/create-server

Create server